Pressure-sensitive adhesive for pressure-sensitive adhesive tape, tape cassette, and tape printer

ABSTRACT

There is provided a double-sided pressure-sensitive adhesive tape which includes a first pressure-sensitive adhesive layer formed by using any of different types of adhesive samples. Thereby the first pressure-sensitive adhesive layer is adjusted so as to satisfy conditions that, slow peel strength when a printing tape made of a PET film is peeled off from the substrate film of the double-sided pressure-sensitive adhesive tape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm or higher and storage modulus of the adhesive layer is in a range from 90.7 kPa to 435 kPa. By improving adhesiveness to the printing tape under environmental temperature from a low temperature to a normal temperature, the double-sided pressure-sensitive adhesive layer renders the printing tape less apt to peel off.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of PCT InternationalPatent Application No. PCT/JP2012/073976 filed on Sep. 20, 2012, whichclaims priority from Japanese Patent Application No. JP 2011-222737,filed on Oct. 7, 2011, the disclosure of which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The disclosure relates to pressure-sensitive adhesive for apressure-sensitive adhesive tape of which adhesiveness to a polyethyleneterephthalate film is improved so as to render the polyethyleneterephthalate film less apt to peel off, a tape cassette accommodatingthe pressure-sensitive adhesive tape and a tape printer employing thetape cassette.

BACKGROUND

As conventional art of this technical field, there has been known a tapecassette for creating a printed tape with a release sheet attachedthereto. In the conventional tape cassette, a laminate film made of apolyethylene terephthalate film, an ink ribbon and a double-sidedpressure-sensitive adhesive tape are separately accommodated in a woundstate. The double-sided pressure-sensitive adhesive tape consists of abase film, a first pressure-sensitive adhesive layer at one side of thebase film and a second pressure-sensitive adhesive layer at the otherside thereof and a release sheet stuck to the second pressure-sensitiveadhesive layer. Of the laminate film, a printed side having been printedby the ink ribbon is stuck to the first pressure-sensitive adhesivelayer of the double-sided pressure-sensitive adhesive tape. Thereby, aprinted tape with a release sheet attached thereto is created.

Regarding the above mentioned double-sided pressure-sensitive adhesivetape to be accommodated in the tape cassette, slow peel strength of thefirst pressure-sensitive adhesive layer on the base film is made higherthan that of the second pressure-sensitive adhesive layer to which therelease sheet is stuck, namely, slow peel strength of the firstpressure-sensitive adhesive layer is made higher than (1 to 10 N/20 mm)at peel rate of 5 mm/minute. The first pressure-sensitive adhesive layerwith the higher slow peel strength is adhered to the laminate film madeof the polyethylene terephthalate film.

A printed tape created by using the above tape cassette, however, hashad a problem such that a laminate film was apt to peel off from a firstpressure-sensitive adhesive layer at an end of the printed tape becausethe first pressure-sensitive adhesive layer's adhesiveness to thelaminate film was still insufficient.

Even if measures for enhancing adhesiveness of the firstpressure-sensitive adhesive layer were taken, a laminate film graduallypeeled off from the first pressure-sensitive adhesive layer of thedouble-sided pressure-sensitive adhesive tape with the passage of time.Therefore, an effective solution has been demanded.

SUMMARY

The disclosure has been made in view of the above mentioned problem andan object thereof is to provide pressure-sensitive adhesive for apressure-sensitive adhesive tape of which adhesiveness to a polyethyleneterephthalate film is improved so as to render the polyethyleneterephthalate film less apt to peel off under environmental temperaturefrom a low temperature to a normal temperature, a tape cassetteaccommodating the pressure-sensitive adhesive tape and a tape printeremploying the tape cassette.

According to the disclosure, there is provided pressure-sensitiveadhesive for a pressure-sensitive adhesive tape, the pressure-sensitiveadhesive being applied on one surface of a substrate film of thepressure-sensitive adhesive tape so as to form a pressure-sensitiveadhesive layer onto which a polyethylene terephthalate film is stuck,wherein the pressure-sensitive adhesive is adjusted so as to satisfyconditions that, slow peel strength when the polyethylene terephthalatefilm is peeled off from the substrate film of the pressure-sensitiveadhesive tape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm orhigher and storage modulus of the adhesive layer is in a range from 90.7kPa to 435 kPa.

Further, according to the disclosure, there is provided a tape cassettefor a tape printer which performs printing on a printing tape by using athermal head, the tape cassette accommodating: a printing tape spool onwhich a printing tape made of a polyethylene terephthalate film iswound; a ribbon spool on which an ink ribbon is wound; and adouble-sided pressure-sensitive adhesive tape spool on which adouble-sided pressure-sensitive adhesive tape which includes a substratefilm, pressure-sensitive adhesive layers formed on both surfaces of thesubstrate film and a release sheet stuck on one of thepressure-sensitive adhesive layers is wound, so that a print image suchas character is formed on the printing tape by the thermal head and theink ribbon while other one of the pressure-sensitive adhesive layers isstuck on the print image, wherein pressure-sensitive adhesive formingthe pressure-sensitive adhesive layers of the double-sidedpressure-sensitive adhesive tape is adjusted so as to satisfy conditionsthat, slow peel strength when the polyethylene terephthalate film ispeeled off from the substrate film of the pressure-sensitive adhesivetape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm or higher andstorage modulus of the adhesive layer is in a range from 90.7 kPa to 435kPa.

Further, according to the disclosure, there is provided a tape printercomprising: a thermal head; a tape cassette accommodating a printingtape spool on which a printing tape made of a polyethylene terephthalatefilm is wound, a ribbon spool on which an ink ribbon is wound, and adouble-sided pressure-sensitive adhesive tape spool on which adouble-sided pressure-sensitive adhesive tape which includes a substratefilm, pressure-sensitive adhesive layers formed on both surfaces of thesubstrate film and a release sheet stuck on one of thepressure-sensitive adhesive layers is wound, so that a print image suchas character is formed on the printing tape by the thermal head and theink ribbon while other one of the pressure-sensitive adhesive layers isstuck on the print image; and a conveyance unit drawing the printingtape, the ink ribbon and the double-sided pressure-sensitive adhesivetape from the printing tape spool, the ink ribbon spool and thedouble-sided pressure-sensitive adhesive tape spool, respectively, forconveyance of those, wherein pressure-sensitive adhesive forming thepressure-sensitive adhesive layers of the double-sidedpressure-sensitive adhesive tape is adjusted so as to satisfy conditionsthat, slow peel strength when the polyethylene terephthalate film ispeeled off from the substrate film of the pressure-sensitive adhesivetape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm or higher andstorage modulus of the adhesive layer is in a range from 90.7 kPa to 435kPa.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tape printer directed to the presentembodiment.

FIG. 2 is a partial enlarged cross-sectional view inside a main bodyframe of the tape printer accommodating a tape cassette therein.

FIG. 3 is a cross-sectional view schematically illustratingconfiguration of a double-sided pressure-sensitive adhesive tape.

FIG. 4 is a table showing values of physical properties measured withrespect to eight types of pressure-sensitive adhesive layers each madeof one of the eight adhesive samples prepared by varying amount ofcrosslinking agent to be added.

FIG. 5 is a graph showing a relation between storage modulus and slowpeel strength with respect to the eight types of pressure-sensitiveadhesive layers each made of one of the eight adhesive samples.

FIG. 6 is a graph showing a relation between storage modulus and thenumber of peeling segments in a polyethylene terephthalate film at 5degrees C. with respect to the eight types of pressure-sensitiveadhesive layers each made of one of the eight adhesive samples.

FIG. 7 is a graph showing a relation between slow peel strength andpeeling length of a polyethylene terephthalate film with respect to theeight types of pressure-sensitive adhesive layers each made of one ofthe eight adhesive samples.

FIG. 8 is a graph showing a relation between storage modulus and peelinglength of a polyethylene terephthalate film with respect to the eighttypes of pressure-sensitive adhesive layers each made of one of theeight adhesive samples.

DETAILED DESCRIPTION

A detailed description of an exemplary embodiment of pressure-sensitiveadhesive for a pressure-sensitive adhesive tape of the disclosure willnow be given referring to the accompanying drawings.

First, schematic configuration of a tape printer directed to the presentembodiment will be described by referring to FIG. 1 and FIG. 2.

A tape printer 1 shown in FIG. 1 includes a main body frame 2, akeyboard 3 arranged in front of the main body frame 2, a printingmechanism PM arranged at the rear inside of the main frame body 2, aliquid crystal display 22 configured to display characters and signs andarranged immediately behind the keyboard 3, and a cover frame 6 forcovering a top surface of the main body frame 2, etc. On the top surfaceof the main body frame 2, there is arranged a release button 4 foropening the cover frame 6 when replacing a tape cassette CS to be set inthe printing mechanism PM. Further, at a side end of the cover frame 6(left-side end in FIG. 1), there is arranged a cutter button 5 forcutting off a printed tape 19 by hand.

The keyboard 3 includes plural operation keys such as character inputkeys for inputting characters, numbers, signs and the like, a space key,a return key, a line feeding key, cursor keys for moving a cursorleftward or rightward, a character-size setting key for arbitrarilysetting font of a to-be-printed character, etc.

Configuration of the printing mechanism PM will be described byreferring to FIG. 2. In the printing mechanism PM, a rectangular-shapedtape cassette CS is accommodated in a replaceable manner. Inside thetape cassette CS, there are rotatably arranged a printing tape spool 8,an ink ribbon spool 10, an ink-ribbon take-up spool 11, a double-sidedpressure-sensitive adhesive tape spool 13 and a bonding roller 14. Theprinting tape spool 8 holds thereon a printing tape 7 made of atransparent polyethylene terephthalate (shortened as PET, hereinafter)film. The ink ribbon spool 10 holds thereon an ink ribbon 9 made of abase film coated with ink which melts when heated. The ink-ribbontake-up spool 11 takes up a used ink ribbon 9. The double-sidedpressure-sensitive adhesive tape spool 13 holds thereon a double-sidedpressure-sensitive adhesive tape 12 having width the same as width ofthe printing tape 7. The double-sided pressure-sensitive adhesive tape12 is wound around there so that a release sheet is located outside. Thebonding roller 14 is used for bonding the printing tape 7 and thedouble-sided pressure-sensitive adhesive tape 12 together. It is to benoted that the double-sided pressure-sensitive adhesive tape 12 consistsof a substrate film, pressure-sensitive adhesive layers on both surfacesof the substrate film and a release sheet stuck on one of thepressure-sensitive adhesive layers (to be described later).

A thermal head 15 is arranged upright at a position where the printingtape 7 and the ink ribbon 9 overlap. A support body 18 is pivotallysupported on the main body frame 2. The support body 18 rotatablysupports a platen roller 16 and a conveyance roller 17. The platenroller 16 is provided for pressing the printing tape 7 and the inkribbon 9 to the thermal head 15. The conveyance roller 17 is providedfor pressing the printing tape 7 and the double-sided pressure-sensitiveadhesive tape 12 to the bonding roller 14 so as to complete a printedtape 19. The thermal head 15 is configured such that heating elementarrays (not shown) consisting of 128 of heating elements are arrangedvertically with reference to a tape surface.

While the bonding roller 14 and the ribbon take-up spool 11 aresynchronously rotated in a predetermined direction by a tape feedingmotor (not shown), the heating element arrays are electrically energizedso that heating elements selectively heated up thereby transmit heatonto the ink ribbon 9. Heat applied by the heating elements melts theink on the ink ribbon 9 and thermally transmits an image onto theprinting tape 7. Thereby, a character or the like is printed on theprinting tape 7 in a form of plural dot lines while the printing tape 7with the double-sided pressure-sensitive adhesive tape 12 bonded theretois conveyed in a tape conveyance direction A as a printed tape 19. Asshown in FIG. 1 and FIG. 2, the printed tape 19 is further conveyed tothe outside (left side in FIG. 1) of the main body frame 2.Incidentally, the configuration of the printing mechanism PM will not bedescribed in detail because the configuration is a heretofore known art.

Next, there will be described a cutter 30 for cutting the printed tape19 by hand, by referring to FIG. 2. Inside the main body frame 2, aplate-like support frame 31 is arranged upright. A fixed blade 32 isdirected upward and fixed to the support frame 31. A pivotal shaft 33fixed to the support frame 31 pivotally supports a near-front endportion of an operation lever 34 which is movable back and forth. Amovable blade 35 is attached to the operation lever 34 at a positionahead of the pivotal shaft 33 located in the operation lever 34 so as toface the fixed blade 32.

A rear end portion of the operation lever 34 is positioned below thecutter button 5. The operation lever 34 is always elastically urged by aspring member (not shown) in a direction to make the movable blade 35stay away from the fixed blade 32. At the front end portion of theoperation lever 34, a cutter switch 41 is arranged so as to detect thatdepression of the cutter button 5 has caused the operation lever 34 topivotally move for cutting operation.

Since the printed tape 19 reaches the outside of the main body frame 2through a space between the fixed blade 32 and the movable blade 35 whenprinting of a character, etc. is completed, depression of the cutterbutton 5 causes the movable blade 32 to approach the fixed blade 35 viathe operation lever 34 and to cut off the printed tape 19.

Next, there will be described a configuration of the double-sidedpressure-sensitive adhesive tape 12 accommodated in the tape cassette CSby referring to FIG. 3.

As shown in FIG. 3, the double-sided pressure-sensitive adhesive tape 12consists of a substrate film 12A made of a PET film; a firstpressure-sensitive adhesive layer 12B formed on one surface (uppersurface in FIG. 3) of the substrate film 12A; a secondpressure-sensitive adhesive layer 12C formed on the other surface of(lower surface in FIG. 3) of the substrate film 12A; and a release sheet12D stuck on the second pressure-sensitive adhesive layer 12C.

It is to be noted that what is depicted above the double-sidedpressure-sensitive adhesive tape 12 is a printing tape 7 made of a PETfilm and that the printing tape 7 and that the first pressure-sensitiveadhesive layer 12B of the double-sided pressure-sensitive adhesive tape12 are bonded together by cooperation of the bonding roller 14 and theconveyance roller 17.

[Embodiment]

Next will be discussed embodiments of the adhesive to be used in thefirst pressure-sensitive adhesive layer 12B and the secondpressure-sensitive adhesive layer 12C according to FIG. 4.

The adhesive composing the first pressure-sensitive adhesive layer 12Band the second pressure-sensitive adhesive layer 12C basically includesan acrylic adhesive agent (AS-5539, available from Ipposha OilIndustries, Co., Ltd.), an isocyanate crosslinking agent (L-45E,available from Nippon Polyurethane Industry Co., Ltd) and aterpene-phenolic tackifier (YS resin TO125, available from YasuharaChemical Co., Ltd.). The content of the isocyanate crosslinking agentwith regard to the acrylic adhesive agent and the terpene-phenolictackifier has been variously adjusted within a range of 0.0 wt. % -2.5wt. % and eight types of adhesive samples, namely, adhesive samples 1-8were prepared.

Here, the content of crosslinking agent is 0.0 wt. % in the adhesivesample 1. The content of crosslinking agent is: 0.1 wt. % in theadhesive sample 2; 0.3 wt. % in the adhesive sample 3; 0.5 wt. % in theadhesive sample 4; 0.7 wt. % in the adhesive sample 5; 1.2 wt. % in theadhesive sample 6; 1.8 wt. % in the adhesive sample 7; and 2.5 wt. % inthe adhesive sample 8.

The storage modulus (kPa) was measured at an ambient temperature of 5degrees C., with regard to eight types of pressure-sensitive adhesivelayers each made of one of the above eight adhesive samples prepared asabove.

The storage modulus of each of the adhesive samples 1-8 was measured asbelow.

(1) Each adhesive of the adhesive samples 1-8 was applied on one side ofa PET film to form a pressure-sensitive adhesive layer thereon, so thata single-sided pressure-sensitive adhesive tape was prepared. Sixteenlayers of the single-sided pressure-sensitive adhesive tapes werelaminated with the PET film of each single-sided pressure-sensitiveadhesive tape positioned upside, without allowing air to entertherebetween. In this state, the PET film was present at the uppermostface of the sixteen layers of the single-sided pressure-sensitiveadhesive tapes.

(2) On top of the PET film at the uppermost face of the sixteen layersof the single-sided pressure-sensitive adhesive tapes stuck together,there was adhered a double-sided pressure-sensitive adhesive tapeprepared through applying the above adhesive of the adhesive samples 1-8on both sides of a PET film to form pressure-sensitive adhesive layersthereon.

(3) Accordingly, seventeen layers were stuck together in total to form alaminate body. The laminate body was punched out into a shape of φ8 mm,using a punch or the like. Thus, measurement objects respectivelycorresponding to the adhesive samples 1-8 were obtained.

(4) Each of the measurement objects obtained as above was set between aplate and parallel plates of a storage-modulus measuring apparatus (anAR-G2 rheometer, available from TA Instruments Ltd.) at a controlledtemperature of 5 degrees C., and was made to move reciprocally androtationally at frequency of 3 Hz and a distortion amount of 0.3 percent, while applying a load of 0.98 N to the parallel plates. Thus, thestorage modulus of a measurement object was measured.

(5) The value of storage modulus measured as above was a value measuredincluding PET films; therefore was converted using a mathematicalformula below in order to eliminate the influence of the PET films, andto obtain the storage modulus of adhesive layers.

$\begin{matrix}{\begin{matrix}{{{{adhesive}'}s}\mspace{14mu}} \\{{storage}\mspace{14mu}{modulus}}\end{matrix} = \frac{\begin{matrix}{{storage}\mspace{14mu}{modulus}\mspace{14mu}{of}\mspace{14mu}{laminate}\mspace{14mu}{body} \times} \\{{total}\mspace{14mu}{thickness}\mspace{14mu}{of}\mspace{14mu}{adhesives}}\end{matrix}}{\begin{matrix}{{total}\mspace{14mu}{thickness}\mspace{14mu}{of}} \\{{PET}\mspace{14mu}{films}\mspace{14mu}{and}\mspace{14mu}{adhesive}}\end{matrix}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

The storage moduli of the eight types of pressure-sensitive adhesivelayers each formed of one of the adhesive samples 1-8 measured by theaforementioned process are shown in FIG. 4. As shown in FIG. 4, thestorage modulus of the adhesive layer is: 62.2 kPa in the adhesivesample 1; 90.7 kPa in the adhesive sample 2; 111.8 kPa in the adhesivesample 3; 186.6 kPa in the adhesive sample 4; 239.6 kPa in the adhesivesample 5; 364.0 kPa in the adhesive sample 6; 409.1 kPa in the adhesivesample 7, and 514.1 kPa in the adhesive sample 8.

Then, slow peel strength was measured with regard to adhesive layersformed on a double-sided pressure-sensitive adhesive tape. Thedouble-sided pressure-sensitive adhesive tape was obtained throughapplying each adhesive of the adhesive samples 1-8 on both sides of asubstrate film made of a PET film to form the adhesive layers thereon.The slow peel strength was measured at ambient temperature of 23±1degrees C., using a measuring apparatus “Autograph AG-IS” available fromShimadzu Corporation, according to the following steps.

(1) First, a surface of a PET film to serve as a measurement surface waswiped and cleaned up with a rag, using ethyl acetate.

(2) A PET film for reinforcement with thickness of 25 μm was bonded ontoan adhesive layer opposite to a surface intended for the measurement ofthe slow peel strength, in the double-sided pressure-sensitive adhesivetape.

(3) An adhesive layer on the measurement surface side of thedouble-sided pressure-sensitive adhesive tape thus reinforced was placedonto the measurement surface of the PET film wiped and cleaned up by therag, and a rubber roller of 3 kg was made to go back and forth threetimes to complete bonding thereof.

(4) Thereafter, the PET film was secured onto a stainless plate (SUSplate) such that the longer direction of the double-sidedpressure-sensitive adhesive tape bonded onto the PET film is verticallyarranged.

(5) After 30 minutes of standing, a lower end of the double-sidedpressure-sensitive adhesive tape in a vertical-state was hooked by ameasurement portion, and was peeled off at an angle of 90 degrees, at aslow peel rate of 0.5 mm/minute in a horizontal direction with regard tothe stainless plate.

(6) The peeling strength when the double-sided pressure-sensitiveadhesive tape was peeled off by 5 mm at the above peeling rate wasmeasured at the measurement portion as the slow peel strength.

The slow peel strength thus measured in connection with the storagemodulus of the eight types of pressure-sensitive adhesive layers eachformed of one of the adhesive samples 1-8 are shown in FIG. 4. A graphshowing a relation between the storage modulus and the slow peelstrength with respect to the eight types of pressure-sensitive adhesivelayers each made of one of the eight adhesive samples is shown in FIG.5. In FIG. 5, the storage modulus and the slow peel strength of theadhesive layer of each of the adhesive samples 1-8 are plotted asabscissae and ordinates, respectively.

In FIG. 4, the slow peel strength of the adhesive layer is: 0.19 N/20 mmin the adhesive sample 1 with the content of the crosslinking agentbeing 0; 0.45 N/20 mm in the adhesive sample 2 with the crosslinkingagent included by 0.1 wt. %; 0.53 N/20 mm in the adhesive sample 3 withthe crosslinking agent included by 0.3 wt. %; 0.54 N/20 mm in theadhesive sample 4 with the crosslinking agent included by 0.5 wt. %;0.64 N/20 mm in the adhesive sample 5 with the crosslinking agentincluded by 0.7 wt. %; 0.63 N/20 mm in the adhesive sample 6 with thecrosslinking agent included by 1.2 wt. %; 0.67 N/20 mm in the adhesivesample 7 with the crosslinking agent included by 1.8 wt. %; and 0.78N/20 mm in the adhesive sample 8 with the crosslinking agent included by2.5 wt. %.

Tendency of the plot shown in the graph of FIG. 5 shows that, among theslow peel strengths of the eight types of pressure-sensitive adhesivelayers each made of one of the adhesive samples 1-8 as measured in theabove, the adhesive layer of the adhesive sample 1 whose slow peelstrength is 0.19 N/20 mm is too weak with regard to adhesive strength toa PET film, and it can be assumed that a printing tape 7 made of a PETfilm will peel off from the first pressure-sensitive adhesive layer 12Bin a short period of time. In contrast, the pressure-sensitive adhesivelayers of the adhesive samples 2-8 have the slow peel strengths with atendency to be discontinuously higher from the slow peel strength of theadhesive layer of the adhesive sample 1, and to gradually increase.Therefore, in order to render the printing tape 7 made of a PET filmless apt to peel off from the first pressure-sensitive adhesive layer12B of the double-sided pressure-sensitive adhesive tape 12 under anenvironment of normal temperature (23±1 degrees C.), it is necessarythat the storage modulus be 90.7 kPa or higher and the slow peelstrength be 0.45 N/20 mm or higher, as in seven types ofpressure-sensitive adhesive layers each made of one of the adhesivesamples 2-8.

Next, the eight types of pressure-sensitive adhesive layers each formedof one of the adhesive samples 1-8 were then measured with regard toadhesiveness at a low temperature of −5 degrees C.

Adhesiveness at a low temperature was measured according to the stepsbelow.

(1) First, each of the adhesive samples 1-8 was applied on both sides ofa substrate film 12A. Thus, there were prepared eight types ofdouble-sided pressure-sensitive adhesive tapes 12 each having a firstpressure-sensitive adhesive layer 12B and a second pressure-sensitiveadhesive layer 12C on both sides of the substrate film 12A.

(2) Each of the eight types of double-sided pressure-sensitive adhesivetapes 12 each corresponding to one of the adhesive samples 1-8 was woundaround double-sided pressure-sensitive adhesive tape spool 13, and thespool 13, a printing tape spool 8 with a printing tape 7 woundedtherearound, an ink ribbon spool 10 with an ink ribbon 9 woundedtherearound, etc. were assembled inside a tape cassette CS. Thus, eighttypes of tape cassettes were produced.

(3) The tape cassettes and a tape printer (PT-9500 available fromBrother Industries, Ltd.) were stored and kept for two hours inside athermostatic chamber controlled at −5 degrees C.

(4) Each tape cassette thus sufficiently-cooled was set inside the tapeprinter and twenty half cuts were continuously provided at an intervalof 20 mm while printing characters, etc. onto the printing tape 7, sothat a printed tape 19 with twenty half-cut segments in the printingtape 7 was prepared. Thus, printed tapes 19 were prepared using theeight types of double-sided pressure-sensitive adhesive tapes 12 eachcorresponding to one of the adhesive samples 1-8.

(5) Immediately after preparing each printed tape 19, there was countedthe number of peeling segments in the printing tape 7 having peeled-offat half cut portions from the first pressure-sensitive adhesive layer12B of the double-sided pressure-sensitive adhesive tape 12 in thethermostatic chamber at −5 degrees C., by visual inspection. A standardfor counting the number of peeling segments in the printing tape 7 issuch that the peeling in a whole width of a segment of the printing tape7 is judged as having peeled off, while the peeling in only a cornerportion of a segment of the printing tape 7 is judged as not havingpeeled off.

FIG. 4 shows correlation of thus- measured adhesiveness at a lowtemperature with thus-measured storage modulus with respect to the eighttypes of pressure-sensitive adhesive layers each formed of one of theadhesive samples 1-8. FIG. 6 is a graph showing a relation betweenstorage modulus and adhesiveness at a low temperature with respect tothe eight types of pressure-sensitive adhesive layers each formed of oneof the adhesive samples 1-8. In FIG. 6, the storage modulus and theadhesiveness at a low temperature (the number of peeling segments in theprinting tape) of each of the adhesive samples 1-8 are plotted asabscissae and ordinates, respectively.

FIG. 4 shows that no observable peeling was found among twenty half-cutsegments in the printing tape 7 of any of the double-sidedpressure-sensitive adhesive tapes 12 of which first adhesive layers 12Bwere formed by using the adhesive samples 1-6. Peeling was observed infour segments among twenty half-cut segments in the printing tape 7 ofthe double-sided pressure-sensitive adhesive tape 12 of which firstpressure-sensitive adhesive layer 12B was formed by using the adhesivesample 7. Peeling was observed in all the twenty half-cut segments inthe printing tape 7 of the double-sided pressure-sensitive adhesive tape12 of which the first pressure-sensitive adhesive layer 12B was formedby using the adhesive sample 8.

Here, the first pressure-sensitive adhesive layer 12B is regarded ashaving better adhesiveness at a low temperature as the number of peelingsegments in a printing tape 7 is smaller. However, taking intoconsideration that partial peeling hardly causes a problem in a segmentof the printing tape 7, different from a case of peeling in a wholewidth, peeling in ten segments in the printing tape 7 or less suggeststhat the first pressure-sensitive adhesive layer 12B has satisfactoryadhesiveness at a low temperature.

Then, if a point of ten peeling segments in a printing tape 7 (anintersection point of the graph and a straight line indicating where tensegments are peeling) is extrapolated in the storage modulus in theabscissae as shown in the graph of FIG. 6, the value of a storagemodulus is 435 kPa.

Thus, it is required of the storage modulus of the pressure-sensitiveadhesive layer to be 435 kPa or lower, as in the pressure-sensitiveadhesive layers of the adhesive samples 1-7, so as to be capable ofpreventing the printing tape 7 from peeling off from the firstpressure-sensitive adhesive layer 12B at a low temperature of −5 degreeC.

One reason for choosing '15 degrees C. as a temperature for measuringthe adhesiveness at a low temperature with respect to the adhesivesamples is that indoor environment temperature can be as low as around−5 degree C. in winter.

The printed tape 19 produced by the tape printer 1 is used by stickingon various kinds of adherends, and the chances are high that it will bestuck onto an adherend having a curved surface. Considering such usage,there was measured a peeling length for the printing tape 7 to peel offfrom the first pressure-sensitive adhesive layer 12B in such asituation.

The peeling length of the printing tape 7 was measured in the followingsteps.

(1) The adhesive samples 1-8 were used to form the first and secondpressure-sensitive adhesive layers 12B and 12C on both sides of thesubstrate film 12A, so as to produce eight types of double-sidedpressure-sensitive adhesive tapes 12. Each of the double-sidedpressure-sensitive adhesive tapes 12 was stuck around an outercircumference of a polypropylene tube of an approximately 5 mm. outerdiameter φ6 mm, with an end portion thereof overlapped by

(2) Each polypropylene tube was stored for 24 hours under an environmentof the temperature of 50 degrees C., and the humidity of 90%.

(3) After storage, the end portion of each of the double-sidedpressure-sensitive adhesive tapes 12 stuck around polypropylene tubeswas observed with a graduated magnifying glass at a room temperature,and peeling length for the printing tape 7 to peel off from the firstpressure-sensitive adhesive layer 12B was measured.

FIG. 4 shows correlation of the length by which the printing tape 7 haspeeled off from the first pressure-sensitive adhesive layers 12B in thedouble-sided pressure-sensitive adhesive tapes 12 with the slow peelstrength with respect to the eight types of pressure-sensitive adhesivelayers each formed of one of the adhesive samples 1-8. A graph showing arelation between the slow peel strength and the peeling length of theprinting tape 7 is shown in FIG. 7. In FIG. 7, the slow peel strengthsof the eight types of pressure-sensitive adhesive layers each made ofone of the adhesive samples 1-8 as mentioned above and the peelinglengths of the printing tapes 7 are plotted as abscissae and ordinates,respectively.

FIG. 4 shows that, in the double-sided pressure-sensitive adhesive tape12 with the first adhesive layer 12B formed by using each of theadhesive samples 3-8, the slow peel strength is 0.53 N/20 mm or higher,and the peeling length for the printing tape 7 to peel off from thefirst pressure-sensitive adhesive layer 12B is 0 mm in the double-sidedpressure-sensitive adhesive tape 12, and no peeling of the printing tape7 is observed. In the double-sided pressure-sensitive adhesive tape 12using the adhesive sample 2 of which the slow peel strength is 0.45 N/20mm, the peeling length for the printing tape 7 to peel off from thefirst pressure-sensitive adhesive layer 12B is 1 mm. Further, in thedouble-sided pressure-sensitive adhesive tape 12 using the adhesivesample 1 of which the slow peel strength is 0.19 N/20 mm, the peelinglength for the printing tape 7 to peel from the first pressure-sensitiveadhesive layer 12B is 5 mm.

The shorter peeling length for the printing tape 7 to peel off from thefirst pressure-sensitive adhesive layer 12B is regarded better; however,the peeling length of 1 mm or shorter is hard to recognize by visualinspection and not conspicuous, therefore the peeling length of 1 mm orshorter is satisfactory.

Then, if a point of 1-mm peeling length of the printing tape 7 (anintersection of the graph and a straight line indicating where thepeeling length is 1 mm) is extrapolated in the storage modulus in theabscissae as shown in the graph of FIG. 7, the value of a slow peelstrength is 0.45 N/20 mm.

Accordingly, considering the chances of the printed tape 19 to be usedbeing stuck onto an adherend having a curved surface, the slow peelstrength of the first pressure-sensitive adhesive layer 12B is 0.45 N/20mm or higher, similar to the pressure sensitive adhesive layers of theadhesive samples 2-8, in order to limit the peeling length of theprinting tape 7 from the first pressure-sensitive adhesive layer 12Bwithin 1 mm or shorter.

Next, regarding the eight types of first pressure-sensitive adhesivelayers 12B each formed of one of the adhesive samples 1-8, a relationbetween thus measured storage modulus and peeling length for theprinting tape 7 to peel off from the first pressure-sensitive adhesivelayer 12B when the double-sided pressure-sensitive adhesive tape 12 isstuck around the tube of an outer diameter φ6 mm is plotted into a graphshown in FIG. 8. In the graph shown in FIG. 8, the storage modulus (kPa)is plotted as abscissae and the peeling length for the printing tape 7to peel off from the first pressure-sensitive adhesive layer 12B whenthe double-sided pressure-sensitive adhesive tape 12 is stuck around thetube of an outer diameter φ6 mm is plotted as ordinates.

As previously mentioned, allowable peeling length for the printing tape7 to peel off from the first pressure-sensitive adhesive layer 12B is 1mm or shorter. It is apparent that the first pressure-sensitive adhesivelayer 12B is required to have storage modulus of 90.7 kPa or higher soas to limit peeling length within 1 mm.

As previously explained, to render the printing tape 7 made of a PETfilm less apt to peel off from a first pressure-sensitive adhesive layer12B of the double-sided pressure-sensitive adhesive tape 12 at a normaltemperature (23±1 degrees C.), it is required for pressure sensitiveadhesive to satisfy conditions such that, storage modulus of the firstpressure-sensitive adhesive layer 12B is 90.7 kPa or higher and slowpeel strength is 0.45 N/20 mm or higher, as each of seven types of thepressure-sensitive adhesive layers formed of any of pressure-sensitiveadhesive samples 2 through 8 satisfies.

Incidentally, to render the printing tape 7 less apt to peel off fromthe first pressure-sensitive adhesive layer 12B at a low temperature (−5degrees C.), it is required for pressure sensitive adhesive to satisfyconditions such that storage modulus of the first pressure-sensitiveadhesive layer 12B is 435 kPa or lower, as each of seven types of thepressure-sensitive adhesive layers formed of any of adhesive samples 1-7satisfies. Further, in consideration of probable situation such that aprinted tape 19 is stuck to an adherend having a curved surface, to keepthe length 1 mm or shorter with respect to peeling length for a printingtape 7 to peel off from a first pressure-sensitive adhesive layer 12B,it is required for pressure-sensitive adhesive to satisfy conditionssuch that, slow peel strength is 0.45 N/20 mm or higher, as each of theseven types of pressure-sensitive adhesive layers formed of any ofpressure-sensitive adhesive samples 2-8 satisfies.

In a case where the first pressure-sensitive adhesive layer 12B of thedouble-sided pressure-sensitive adhesive tape 12 is formed by using anyof adhesive samples 2-7, slow peel strength when the printing film 7made of a PET film is peeled off from the first pressure-sensitiveadhesive layer 12B is 0.45 N/20 mm or higher and storage modulus of thefirst pressure-sensitive adhesive layer 12B is 90.7 kPa or higher undera normal temperature (23±1 degrees C.) and 435 kPa or lower under a lowtemperature (−5 degrees C.).

Accordingly, when the first pressure-sensitive adhesive layer 12B of thedouble-sided pressure-sensitive adhesive tape 12 is formed by using anyof pressure adhesive samples 2-7, the first pressure-sensitive adhesivelayer 12B thus formed can render the printing tape 7 less apt to peeloff under environmental temperature from a low temperature (−5 degreesC.) to a normal temperature (23±1 degrees C.) even if the secondpressure sensitive layer 12C is stuck to an adherend having a curvedsurface.

As described in the above, pressure-sensitive adhesive constituting thefirst pressure-sensitive adhesive layer 12B of the double-sidedpressure-sensitive adhesive tape 12 directed to the embodiment is formedby using any of adhesive samples 2-7 so that the firstpressure-sensitive adhesive layer 12B satisfies conditions such that,slow peel strength when the printing film 7 made of a PET film is peeledoff from the substrate film 12A of the double-sided pressure-sensitiveadhesive tape 12 by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mmor higher and storage modulus of the first pressure-sensitive adhesivelayer 12B is in a range from 90.7 kPa to 435 kPa. Since adhesiveness tothe printing tape 7 under environmental temperature from a lowtemperature to a normal temperature is thus improved, thepressure-sensitive adhesive renders the printing tape 7 less apt to peeloff.

Regarding the tape cassette CS directed to the embodiment, thepressure-sensitive adhesive constituting the first pressure-sensitiveadhesive layer 12B of the double-sided pressure-sensitive adhesive tape12 is formed by using any of pressure sensitive adhesive samples 2-7 sothat the first pressure-sensitive adhesive layer 12B satisfiesconditions such that, slow peel strength when the printing film 7 madeof a PET film is peeled off from the substrate film 12A of thedouble-sided pressure-sensitive adhesive tape 12 by 5 mm at peel rate of0.5 mm/minute is 0.45 N/20 mm or higher and storage modulus of the firstpressure-sensitive adhesive layer 12B is in a range from 90.7 kPa to 435kPa. Since adhesiveness to the printing tape 7 under environmentaltemperature from a low temperature to a normal temperature is thusimproved, the pressure-sensitive adhesive renders the printing tape 7less apt to peel off when the first pressure-sensitive adhesive layer12B on the substrate film 12A is stuck to a print image such ascharacter formed on the printing tape 7 by the thermal head 15 and theink ribbon 9.

Regarding the tape printer 1 directed to the embodiment,pressure-sensitive adhesive constituting the first pressure-sensitiveadhesive layer 12B of the double-sided pressure-sensitive adhesive tape12 is formed by using any of pressure sensitive adhesive samples 2through 7 so that the pressure-sensitive adhesive layer 12B satisfiesconditions such that, slow peel strength when the printing film 7 madeof a PET film is peeled off from the substrate film 12A of thedouble-sided pressure-sensitive adhesive tape 12 by 5 mm at peel rate of0.5 mm/minute is 0.45 N/20 mm or higher and storage modulus of the firstpressure-sensitive adhesive layer 12B is in a range from 90.7 kPa to 435kPa. Since adhesiveness to the printing tape 7 under environmentaltemperature from a low temperature to a normal temperature is thusimproved, the pressure-sensitive adhesive renders the printing tape 7less apt to peel off when the printing tape 7 is conveyed by theconveyance roller 17 and the first pressure-sensitive adhesive layer 12Bon the substrate film 12A of the double-sided pressure-sensitiveadhesive tape 12 is stuck to a print image such as character formed onthe printing tape 7 by the thermal head 15 and the ink ribbon 9.Especially, even if a release sheet 12D is peeled off from a printedtape 19 created by the tape printer 1 and the second pressure-sensitiveadhesive layer 12C on the substrate film 12A is stuck on an adherendhaving a curved surface, the pressure-sensitive adhesive can render theprinting tape 7 less apt to peel off from the first pressure-sensitiveadhesive layer 12B on the substrate film 12A. Therefore, visual neatnessof the printed tape 19 stuck on the adherend having a curved surface canbe kept for a long period of time.

While presently exemplary embodiments has been shown and described, itis to be understood that this disclosure is for the purpose ofillustration and that various changes and modifications may be madewithout departing from the scope of the disclosure as set forth in theappended claims.

The disclosure provides pressure-sensitive adhesive for apressure-sensitive adhesive tape of which adhesiveness to a polyethyleneterephthalate film is improved so as to render the polyethyleneterephthalate film less apt to peel off under environmental temperaturefrom a low temperature to a normal temperature, a tape cassetteaccommodating the pressure-sensitive adhesive tape and a tape printeremploying the tape cassette. The effect which the disclosure brings tothe applicable industrial field is significant.

What is claimed is:
 1. Pressure-sensitive adhesive for apressure-sensitive adhesive tape, the pressure-sensitive adhesive beingapplied on one surface of a substrate film of the pressure-sensitiveadhesive tape so as to form a pressure-sensitive adhesive layer ontowhich a polyethylene terephthalate film is stuck, wherein thepressure-sensitive adhesive is adjusted so as to satisfy conditionsthat, slow peel strength when the polyethylene terephthalate film ispeeled off from the substrate film of the pressure-sensitive adhesivetape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm or higher andstorage modulus of the adhesive layer is in a range from 90.7 kPa to 435kPa.
 2. A tape cassette for a tape printer which performs printing on aprinting tape by using a thermal head, the tape cassette accommodating:a printing tape spool on which a printing tape made of a polyethyleneterephthalate film is wound; a ribbon spool on which an ink ribbon iswound; and a double-sided pressure-sensitive adhesive tape spool onwhich a double-sided pressure-sensitive adhesive tape which includes asubstrate film, pressure-sensitive adhesive layers formed on bothsurfaces of the substrate film and a release sheet stuck on one of thepressure-sensitive adhesive layers is wound, so that a print image suchas character is formed on the printing tape by the thermal head and theink ribbon while other one of the pressure-sensitive adhesive layers isstuck on the print image, wherein pressure-sensitive adhesive formingthe pressure-sensitive adhesive layers of the double-sidedpressure-sensitive adhesive tape is adjusted so as to satisfy conditionsthat, slow peel strength when the polyethylene terephthalate film ispeeled off from the substrate film of the pressure-sensitive adhesivetape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm or higher andstorage modulus of the adhesive layer is in a range from 90.7 kPa to 435kPa.
 3. A tape printer comprising: a thermal head; a tape cassetteaccommodating a printing tape spool on which a printing tape made of apolyethylene terephthalate film is wound, a ribbon spool on which an inkribbon is wound, and a double-sided pressure-sensitive adhesive tapespool on which a double-sided pressure-sensitive adhesive tape whichincludes a substrate film, pressure-sensitive adhesive layers formed onboth surfaces of the substrate film and a release sheet stuck on one ofthe pressure-sensitive adhesive layers is wound, so that a print imagesuch as character is formed on the printing tape by the thermal head andthe ink ribbon while other one of the pressure-sensitive adhesive layersis stuck on the print image; and a conveyance unit drawing the printingtape, the ink ribbon and the double-sided pressure-sensitive adhesivetape from the printing tape spool, the ink ribbon spool and thedouble-sided pressure-sensitive adhesive tape spool, respectively, forconveyance of those, wherein pressure-sensitive adhesive forming thepressure-sensitive adhesive layers of the double-sidedpressure-sensitive adhesive tape is adjusted so as to satisfy conditionsthat, slow peel strength when the polyethylene terephthalate film ispeeled off from the substrate film of the pressure-sensitive adhesivetape by 5 mm at peel rate of 0.5 mm/minute is 0.45 N/20 mm or higher andstorage modulus of the adhesive layer is in a range from 90.7 kPa to 435kPa.